Streamflow Changes in the Vicinity of Seismogenic Fault After the 1999 Chi–Chi Earthquake

2018 ◽  
pp. 19-28
Author(s):  
Ching-Yi Liu ◽  
Yeeping Chia ◽  
Po-Yu Chuang ◽  
Chi-Yuen Wang ◽  
Shemin Ge ◽  
...  
Keyword(s):  
Seismogenic Fault

scholarly journals Analysis of the Impact of Fault Mechanism Radiation Patterns on Macroseismic Fields in the Epicentral Area of 1998 and 2004 Krn Mountains Earthquakes (NW Slovenia)

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Andrej Gosar
Keyword(s):  
Site Effects ◽  
Strike Slip ◽  
Radiation Patterns ◽  
Seismogenic Fault ◽  
Active Growth ◽  
Epicentral Area ◽  
Slip Mechanism ◽  
Radiation Amplitude ◽  
The Difference ◽  
The Impact

Two moderate magnitude (Mw = 5.6 and 5.2) earthquakes in Krn Mountains occurred in 1998 and 2004 which had maximum intensity VII-VIII and VI-VII EMS-98, respectively. Comparison of both macroseismic fields showed unexpected differences in the epicentral area which cannot be explained by site effects. Considerably, different distribution of the highest intensities can be noticed with respect to the strike of the seismogenic fault and in some localities even higher intensities have been estimated for the smaller earthquake. Although hypocentres of both earthquakes were only 2 km apart and were located on the same seismogenic Ravne fault, their focal mechanisms showed a slight difference: almost pure dextral strike-slip for the first event and a strike-slip with small reverse component on a steep fault plane for the second one. Seismotectonically the difference is explained as an active growth of the Ravne fault at its NW end. The radiation patterns of both events were studied to explain their possible impact on the observed variations in macroseismic fields and damage distribution. Radiation amplitude lobes were computed for three orthogonal directions: radial P, SV, and SH. The highest intensities of both earthquakes were systematically observed in directions of four (1998) or two (2004) large amplitude lobes in SH component (which corresponds mainly to Love waves), which have significantly different orientation for both events. On the other hand, radial P direction, which is almost purely symmetrical for the strike-slip mechanism of 1998 event, showed for the 2004 event that its small reverse component of movement has resulted in a very pronounced amplitude lobe in SW direction where two settlements are located which expressed higher intensities in the case of the 2004 event with respect to the 1998 one. Although both macroseismic fields are very complex due to influences of multiple earthquakes, retrofitting activity after 1998, site effects, and sparse distribution of settlements, unusual differences in observed intensities can be explained with different radiation patterns.

Complex Slip Distribution of the 2021 Mw 7.4 Maduo, China, Earthquake: An Event Occurring on the Slowly Slipping Fault

2021 ◽  
Author(s):  
Rumeng Guo ◽  
Hongfeng Yang ◽  
Yu Li ◽  
Yong Zheng ◽  
Lupeng Zhang
Keyword(s):  
Slip Rate ◽  
Slip Distribution ◽  
Seismic Gap ◽  
Seismogenic Fault ◽  
Coseismic Slip ◽  
Slip Rates ◽  
Kunlun Mountain ◽  
Coulomb Failure ◽  
Main Fault ◽  
Large Earthquakes

Abstract The 21 May 2021 Maduo earthquake occurred on the Kunlun Mountain Pass–Jiangcuo fault (KMPJF), a seismogenic fault with no documented large earthquakes. To probe its kinematics, we first estimate the slip rates of the KMPJF and Tuosuo Lake segment (TLS, ∼75 km north of the KMPJF) of the East Kunlun fault (EKLF) based on the secular Global Positioning System (GPS) data using the Markov chain Monte Carlo method. Our model reveals that the slip rates of the KMPJF and TLS are 1.7 ± 0.8 and 7.1 ± 0.3 mm/yr, respectively. Then, we invert high-resolution GPS and Interferometric Synthetic Aperture Radar observations to decipher the fault geometry and detailed coseismic slip distribution associated with the Maduo earthquake. The geometry of the KMPFJ significantly varies along strike, composed of five fault subsegments. The most slip is accommodated by two steeply dipping fault segments, with the patch of large sinistral slip concentrated in the shallow depth on a simple straight structure. The released seismic moment is ∼1.5×1020  N·m, equivalent to an Mw 7.39 event, with a peak slip of ∼9.3 m. Combining the average coseismic slip and slip rate of the main fault, an earthquake recurrence period of ∼1250−400+1120  yr is estimated. The Maduo earthquake reminds us to reevaluate the potential of seismic gaps where slip rates are low. Based on our calculated Coulomb failure stress, the Maduo earthquake imposes positive stress on the Maqin–Maqu segment of the EKLF, a long-recognized seismic gap, implying that it may accelerate the occurrence of the next major event in this region.

Wave conversions from earthquakes and a new velocity model for the South Carolina coastal plain

1987 ◽  
Vol 77 (6) ◽  
pp. 2143-2151
Author(s):  
Susan Rhea
Keyword(s):  
Surface Layer ◽  
South Carolina ◽  
Coastal Plain ◽  
Velocity Structure ◽  
Velocity Model ◽  
Seismogenic Fault ◽  
Impedance Boundary ◽  
High Impedance ◽  
Hypocentral Parameters ◽  
Converted Phases

Abstract Phase conversions from P to SV and from SV to P occur at a high impedance boundary near the surface in Charleston, South Carolina. Four arrivals (P, converted P, converted S, and S) are observed on three-component records of earthquakes in this area. Using arrival-time differences between paired arrivals of direct and converted phases, a shallow surface layer Vp/Vs ratio of 2.9 was determined. Applying the Wadati method to travel times derived at the base of the surface layer yields a Vp/Vs ratio in deeper layers of 1.73. Relocating earthquakes using this more appropriate velocity structure for direct and converted shear waves alters hypocentral parameters such that epicenters diverge and depths converge. It is inferred that these relocated earthquakes are not exclusively associated with a single seismogenic fault.

scholarly journals Fault “Corrosion” by Fluid Injection: A Potential Cause of the November 2017 MW 5.5 Korean Earthquake

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-23 ◽  
Author(s):  
Rob Westaway ◽  
Neil M. Burnside
Keyword(s):  
Time Delays ◽  
Chemical Properties ◽  
Fluid Injection ◽  
Anthropogenic Activity ◽  
Geothermal System ◽  
Causal Mechanism ◽  
Seismogenic Fault ◽  
Subsurface Environment ◽  
Anthropogenic Seismicity ◽  
Physical And Chemical

The November 2017 MW 5.5 Pohang earthquake is one of the largest and most damaging seismic events to have occurred in the Korean peninsula over the last century. Its close proximity to an Enhanced Geothermal System (EGS) site, where hydraulic injection into granite had taken place over the previous two years, has raised the possibility that it was anthropogenic; if so, it was by far the largest earthquake caused by any EGS project worldwide. However, a potential argument that this earthquake was independent of anthropogenic activity considers the delay of two or three months before its occurrence, following the most recent injection into each of the wells. A better understanding of the physical and chemical processes that occur following fluid injection into granite is thus warranted. We show that hydrochemical changes occurring while surface water, injected into granite, reequilibrates chemically with its subsurface environment, can account for time delays for earthquake occurrence of such duration, provided the seismogenic fault was already critically stressed, or very close to the condition for slip. This candidate causal mechanism counters the potential argument that the time delay militates against an anthropogenic cause of the Pohang earthquake and can account for its relatively large magnitude as a consequence of a relatively small-volume injection. The resulting analysis places bounds on combinations of physical and chemical properties of rocks, injected volume, and potential postinjection time delays for significant anthropogenic seismicity during future EGS projects in granite.

scholarly journals Pore Pressure Analysis for Distinguishing Earthquakes Induced by CO2 Injection from Natural Earthquakes

2020 ◽  
Vol 12 (22) ◽  
pp. 9723
Author(s):  
Chanmaly Chhun ◽  
Takeshi Tsuji
Keyword(s):  
Pore Pressure ◽  
Co2 Storage ◽  
Carbon Capture And Storage ◽  
Co2 Injection ◽  
Storage Site ◽  
Seasonal Fluctuations ◽  
Induced Earthquakes ◽  
Seismogenic Fault ◽  
Seismogenic Faults ◽  
Natural Earthquakes

It is important to distinguish between natural earthquakes and those induced by CO2 injection at carbon capture and storage sites. For example, the 2004 Mw 6.8 Chuetsu earthquake occurred close to the Nagaoka CO2 storage site during gas injection, but we could not quantify whether the earthquake was due to CO2 injection or not. Here, changes in pore pressure during CO2 injection at the Nagaoka site were simulated and compared with estimated natural seasonal fluctuations in pore pressure due to rainfall and snowmelt, as well as estimated pore pressure increases related to remote earthquakes. Changes in pore pressure due to CO2 injection were clearly distinguished from those due to rainfall and snowmelt. The simulated local increase in pore pressure at the seismogenic fault area was much less than the seasonal fluctuations related to precipitation and increases caused by remote earthquakes, and the lateral extent of pore pressure increase was insufficient to influence seismogenic faults. We also demonstrated that pore pressure changes due to distant earthquakes are capable of triggering slip on seismogenic faults. The approach we developed could be used to distinguish natural from injection-induced earthquakes and will be useful for that purpose at other CO2 sequestration sites.

Dynamic Rupture Simulations of the 1920 Ms 8.5 Haiyuan Earthquake in China

2019 ◽  
Vol 109 (5) ◽  
pp. 2009-2020 ◽  
Author(s):  
Xiurong Xu ◽  
Zhenguo Zhang ◽  
Feng Hu ◽  
Xiaofei Chen
Keyword(s):  
Ground Motion ◽  
Intensity Distribution ◽  
Strong Ground Motion ◽  
Ground Surface ◽  
Peak Ground Velocity ◽  
The Tibetan Plateau ◽  
Dynamic Rupture ◽  
Seismogenic Fault ◽  
Maximum Displacement ◽  
Strong Ground

Abstract The Haiyuan fault is a major seismogenic fault on the northeastern edge of the Tibetan–Qinghai plateau. The 16 December 1920 Ms 8.5 Haiyuan, China, earthquake is the largest and most recent event along the eastern Haiyuan fault (the Haiyuan fault in the article). Because only a few near‐field seismic recordings are available, the rupture process remains unclear. To understand the source process and intensity distribution of the 1920 Haiyuan earthquake, we simulated the dynamic rupture and strong ground motion of said earthquake using the 3D curved‐grid finite‐difference method. Considering the differences in epicenter locations among various catalogs, we constructed two models with different source points. For each model, three versions with different fault geometries were investigated: one continuous fault model and two discontinuous fault models with different stepover widths (1.8 and 2.5 km, respectively). A dynamic rupture source model with a final slip distribution similar to that observed on the ground surface was found. The maximum displacement on the ground surface was ∼6.5  m. Based on the dynamic rupture model, we also simulated the strong ground motion and estimated the theoretical intensity distribution. The maximum value of the horizontal peak ground velocity occurs near Haiyuan County, where the intensity reaches XI. Without considering the site conditions, the intensity values in most regions, based on the dynamic scenarios, are smaller than the values from field investigation. In this work, we present physically based insights into the 1920 Haiyuan earthquake, which is important for understanding rupture processes and preventing seismic hazards on the northeastern boundary of the Tibetan plateau.

scholarly journals Characteristic scales of earthquake rupture from numerical models

2003 ◽  
Vol 10 (6) ◽  
pp. 573-584 ◽  
Author(s):  
M. H. Heimpel
Keyword(s):  
Numerical Models ◽  
Three Dimensional ◽  
Characteristic Size ◽  
Strength Distribution ◽  
Earthquake Rupture ◽  
Size Distributions ◽  
Seismogenic Fault ◽  
Smooth Model ◽  
Heterogeneous Models ◽  
Asperity Model

Abstract. Numerical models of earthquake rupture are used to investigate characteristic length scales and size distributions of repeated earthquakes on vertical, planar fault segments. The models are based on exact solutions of static three-dimensional (3-D) elasticity. Dynamical rupture is approximated by allowing the static stress field to expand from slip motions at a single velocity. To show how the vertical fault width affects earthquake size distributions for a broad range of fault behaviors, two different fault strength models are used; a smooth model and a heterogeneous asperity model. The smooth model is a simplified version of the Dieterich-Ruina rate and state dependent friction law. The heterogeneous asperity model uses a slip-dependent random powerlaw strength distribution. It is shown that the characteristic scale of fault segmentation is proportional to the vertical width of a seismogenic fault. This conclusion holds for both the smooth and the heterogeneous models. For the smooth models characteristic quake distributions result, with populations of large events that are obviously distinct from smaller events. The distributions of large events have well-defined mean lengths and moments. The heterogeneous models result in Gutenberg-Richter (GR) powerlaw distributions of event sizes up to a characteristic quake size. Quakes larger than the characteristic size fall off the GR distribution such that the powerlaw would greatly overestimate the probability of occurrence of the larger events.

Sequential modelling of the 2016 Central Italy earthquake cluster using multisource satellite observations and quantitative assessment of Coulomb stress change

2020 ◽  
Vol 221 (1) ◽  
pp. 451-466 ◽  
Author(s):  
Qian Xu ◽  
Qiang Chen ◽  
Jingjing Zhao ◽  
Xianwen Liu ◽  
Yinghui Yang ◽  
...  
Keyword(s):  
Surface Deformation ◽  
Central Italy ◽  
Normal Fault ◽  
Satellite Observations ◽  
Fault System ◽  
Potential Zone ◽  
Seismic Zone ◽  
Seismogenic Fault ◽  
Positive Effects ◽  
Sequence Of Events

SUMMARY A sequence of earthquake events consisting of three large shocks occurred in Central Italy from August to October in 2016 with the duration of almost 2 months. The preliminary study on the seismic mechanism suggests that the sequence of events is the result from the activity of the SW dipping Mt Bove–Mt Vettore–Mt Gorzano normal fault system. For investigation and understanding of the coseismic faulting of the seismogenic fault alignment, we collect a set of comprehensive satellite observations including the Sentinel-1A, ALOS-2/PALSAR-2 and GPS data to map the coseismic surface deformation and estimate the source models in this study. The derived faulting model for the first Amatrice event is characterized by two distinct slip asperities suggesting that it is a predominantly normal dip-slip motion with slight strike-slip component. The second event, Visso earthquake is almost a purely normal rupture. The third Norcia event is dominated by the normal dip-slip rupture of the seismogenic fault, and has propagated up to the ground with significant slip. The three faulting models are then utilized to quantify the Coulomb failure stress (CFS) change over the seismic zone. First, the CFS change on the subsequent two seismogenic faults of the earthquake sequence is estimated, and the derived positive CFS change induced by the preceding earthquakes suggests that the early events have positive effects on triggering the subsequent seismicity. We then explore the response relation of the aftershocks including 961 events with magnitudes larger than M 3.0 to the CFS change over the seismic zone. It suggests that the rupture pattern of the aftershocks is similar to the major shocks with predominantly normal dip-slip. To assess the risk of the future seismic hazard, we analyse quantitatively the spatial distribution of aftershock occurrence and CFS transfer at the seismogenic depth, indicating that the ruptures of the three major shocks do partly release the accumulated strain on the associated fault alignment as well as the dense aftershock, but the CFS increase zone with few aftershocks in the southwest of the eastern Quaternary fault alignment of Central Italy poses the potential of further rupture. In particular, the distribution of aftershock migration also suggests that the north extension of the Mt Bove fault is the potential zone with rupture risk.

scholarly journals Spatial Variation in the Slip Zone Thickness of a Seismogenic Fault

2018 ◽  
Vol 45 (15) ◽  
pp. 7542-7550 ◽  
Author(s):  
J. D. Kirkpatrick ◽  
K. A. H. Shervais ◽  
M. J. Ronayne
Keyword(s):  
Spatial Variation ◽  
Slip Zone ◽  
Seismogenic Fault
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